He has shown honesty and good morals before (alongside his imperfect entrepreneurship). I think it's either about a grave accident (such as losing private keys) or a US govt. instance having pulled string in Japan, having seized their assets. Karpelès said (confirmed) already days ago in response to an internal discussion that "the US govt. doesn't want us to talk about it", which makes me believe it's indeed about seized assets, and that it's connected to the misguided suspicion that they had something to do with Silk Road.

So this is actually a test of the one of the attractive principles of Bitcoin: no one can separate you from your money, assuming that you control your private keys. Karpeles isn't a complete idiot, so I'm certain the keys to what balance he himself maintains are safely stored somewhere only he knows (brain wallet?). So, assuming that he has substantial holdings in bitcoin, then what good does the asset freeze do? He is free to spend bitcoin, unless the asset freeze also prevents businesses from accepting money of any kind from him.

Same holds for the two companies, but they are much more likely to have a larger USD balance that is actually affected by the freeze.